Draft-gage



Patented Dec. 7, 1920.

L. COOK.

DRAFT GAGE.

APPLICATION FILED JUNE 1, 1918.

" YIJIVII/IIVINTOR.

\ I I I A TTORNEYS.

UNITED STATES PATENT OFFICE.

LEWIS 000K, or OAK PARK, ILLINOIS.

DRAFT- GAGE.

To all whom it may concern Be it known that I, LEwIs COOK, a citizen of the United States of America, and a resident of Oak Park, county of Cook, and. 6 State of Illinois, have invented certain new The main objects of this invention are to provide in gages of the U-tube type wherein the pressure is indicated by the position of the surface of a liquid in a glass tube, certain means, whereby adjustments may be made to readily compensate for the variations of diameter that commonly occur in commercial glass tubes; to provide improved means for readily adjusting such gages to conform to a standard scale, thereby obviating the necessity of preparing a 25 special scale for each gage where great .accuracy is required or the alternative necessityof makingthe tubes conform exactly to predetermined dimensions; and to provide improved means for adjusting the relative angular disposition of the legs of the U- tube.

In gages of this general type where the gage leg of the tube is inclined to the hori zontal in order to indicate minute difierences of pressure, such leg must be of relatively small diameter in order to insure that the exposed surface of the liquid therein shall form a meniscus approximately at right angles to the axis of the tube instead of stand- 40 ing substantially horizontal as in a large tube. To this end, it is a further object of this invention to provide an improved .con-

struction whereby the gage-tube may be of 5 small diameter and be supplemented by an such as to require a larger sectional area for the respective leg of the tube, than 'would produce the right kind of a meniscus.

, Referring to the drawings, Figure 1 is a front elevation of a specific embodiment of this invention as applied to a draft-gage of the type used in indicating furnace efficiency. 4

Fig. 2 is a detail in plan and partly in section, showing the arrangement of the aux- Specification of Letters Patent.

additional tube, when the conditions are.

Patented Dec. '7, 1920 Application filed June 1, 1918. Serial No. 237,721.

iliary tube behind the gage-tube in the device shown in Fi 1.

Fig. 3 is a detall ofa modified formof U- tube.

Fig. 4 is a detail of a liner which is used 60 for adjusting the area of the interior of the large leg or bottle.

Fig. 5 is a perspective view of an adjusting level which is used for accurately setting the gageglass while the device is being assembled.

The form shown in the drawings is a draft gage of a type used in determining furnace efficiencies and in general comprises two U- tubes designated 1 and 2, the ,tube 2 being arranged for measuring the difference in pressures between thev atmosphere and the 7 inside .of the furnace above the fuel bed, whereas the tube 1 is arranged for measuring the pressures between the inside of-the furnace above the fuel bed and the chimney;

In the specific form shown, the U-tubes are mounted within a casing 3 which is secured to the outside of the fufnace by means of ascrew at 4, and after being leveled up\ by means of a level 5 is. fixed by means of screws at 6 and 7 The indicating legs 8 and 9 of the U- tubes are inclined at a slight angle from a horizontal position, and in order to indicate the small differences of pressure which the. instrument is designed to measure, are pro I Vided with a scale 10 preferably graduatedto read in. tenths of an inch of water head. The scale 10 is of a standard construction so far as its use with devices of this kind and for this pur ose is concerned. w The tubes are partly fill ed with oil of suitable specific gravity, and the quantity of oil is exactly measured so as to bring the liquid levels in the indicating tubes at zero on the scale when both legs of the tubes are at atmospheric pressure.

The other legs of the tubes are preferably vertical and are of considerably larger diameter than the indicating legs, so as to insure a' long range ofmovement of the indicating liquid level for slight differences ofhead. I g- It has been customary in the manufacture of gages of this general type to make the indicating legs and the vertical legs or hottles of the U-tubes out ofa single P1806 of glass, which must be made with great accuracy in order to avoid the necessity of preparing a special scale for each instrubottles 11 and 12 which constitute the vertical legs of the U-tubes 1 and 2 respectively are made of metal of standard size, and the inclined legs 8 and 9 are glass tubes which may vary slightly in diameter, as in the case with commercial lass tubin The tubes leadlng upwar from the bottles 11 and 12 are preferably extended into the bottles so as to serve to hold the liners 13 in upright positions against the sides of the bottles where they will not interfere with filling or emptying-the bottles. Drain openings 13.1 are positioned so as to insure that none of the oil will be entrained when the device is inverted for emptying it.

The bottles 11 are made of slightlylarger diameter than that which is correct for the particular size of glass tube which is used, and adjustment between the areas of the exposed surfaces in the two tubes is effected by inserting into the bottles verticallydis osed liners or filler members 13 which are 0 uniform cross section throughout the range of movement of the liquid levels in the bottles.

-The filler members are preferably made of tubes are cemented into sockets 14 by means of an adhesive plastic composition, such as litharge and glycerin, which is insoluble in lead or other non-corrodible metalwhich can be read ly bent to conform to the curveture of the, walls of the bottle. The glass I oil or water and makes an air-tight joint.

for securing the gage in its casing and em bedding all joints to make them liquid and air-ti ht;

Be ore assembling the device, a quantity of liquid is poured into the bottle until the level thereof in the glass tube is'exactly at zero on the scale at atmospheric ressure, and the device is then calibrated or other pressures by inserting one or more fillers of suitable sectional area so that the liquid level Wlll cometo the highest reading on thesca'le, i v

-' of a glass tube of the largest size that would which in the device shown is one inch of water head when it is subjected to a correspondis preferably done in a suitable testing ap-' ingdifierence of pressure. This calibrating aratus after-the bottle and gage tubehave n connected to ether, but before thecaps and pressure tu es are soldered orotherwise secured. in lace on the bottle. Once the device is cali rated for a certain range of pressures, there is no need of removing or cha the fillers. -Where, however, it is desirable to have the same gage readily ad- I justable for different ranges of pressure, it

- tinguish them.

with the glass tube and directly be should preferably be of theform shown in Fi .3 hereinafter described. x

gravity of the liquid used and the pressure rangewhich is to be indicated. Therefore,

one of the U-tubes is first fastened into the instrument case with its indicating leg parassembling meters in which the tubes have adifferent' slant. The level tube 17 may, for

example, have a slant coresponding to "an instrument designed for natural draft furnaces yvhereas the slant of the level tube 17.1

may be for a gage designed for forced draft furnaces. Adjacent level tubes 17 and 17 .1 are laced characters C and"D respectlvely toenable the liser to readily dis- The U-tube 2 is provided with 'a connec tion 19 of-semi-rigid tubing made of'soft metal which may be readily bent so as to bring the indicating tube 9 parallel with the indicating tube 8. To insure accurate setting of I he slant of the indicatinglegs is prede-' ter'mined in accordance with the specific the glass tube 9, even though it be not ex" actly. straight, the device 15 is again employed as above described. Thereafter, all

' that is necessary to set up the instrument is .to hang the-casm'g so that the bubble in the level tube '5 indicates that. the same is level, and then to connect the pipes 20 and 21 with the chimney and furnace respectively.

The transparent indicating tubes should be of small enough diameter to insure that the exposed surface of the liquid therein will stand inthe form of a meniscus substantially at right angles to the ax1s of the respectivetube, so that the indication maybe.

read with certainty upon the scale.

Ifthe range 'of pressures is such that it is" desirable to use a liquid column of greater sectional area in the indicating'leg of the U-tube than the sectional area of thebore have .a roper meniscus, this may be accom 'plished y placing behind the indicating tube parallel ind it at oints along the scale. This is connected ii the bottle 12 by means of a bendable an auxiliary tube 22 which is exactly all wit metal tube 23, and the tubes 9 and 22 are forced draft furnace.

Exact adjustment may inthis case be ob-;-- tained by inserting fillers '25 or 13 .'respectively into the tube 22' 0r the bottle 12 as may be required until the combined sectional area of the tubes 19 and 22 will be correct with re spect to the sectional area of the leg 12 of the I To facilitate this, oneend .of the tube 22 may be provided with 'aremovable cap-26. 1

-In Fig. 3,-a modification is shown wherein the parts may be readily taken apart for cleaning or repairing'and the vertical leg of theU-tube-is made'of two tubes 27 and 28 whereby adjustment of the sectional area of said leg may be accomplished by fillers confined in the bottle 27 leaving the tube 28 clear for inserting a small brass tube used for removing oil to adjust the liquid level.

.1 Union fittings 31 maybe employed at suitable pointsto enable the parts to be separated for convenience in cleaning them. The tubes 27 and 28 communicate'with each other both" at the top and bottom throu h the tubular connections 32. Y This form-o the invention is particularly advantageous for use in, instances where it maybe desirable at times to change the instrument for. use in connect1on w th one range of pressures to another a range. In this form, the bottle 27 would be arranged in'the. instrument case in such a way that the cap 33 at the upper end thereof would be readily accessible to permit there.

movaland insertion of filler strips 13.

The device may be equipped withslidable indicator plates 29 and provided with ar- .rowstov indicate the normal-position of the indicating. column of liquid for maximum efliciency of the particular furnace towhich the device is applied, and -insuflicie ncy or. superabundance of air flow is indicated thereon by means of minus and plus signs on the plates.

The use of liners or fillers for adjusting therange .of movement of the oil in the indicator tube provides any desired degree of adjustment since these fillers may --range from fine wire-up to large strips, as illustrated in Fig. 4'. By this-means it is possible to adjust; the gage so-that theentire'length of the scale, say ten inches, can. be used. to register "a relatively low range of pressures 'such as 0f an inch of water head,-or to register a relat vely high range such as 10 inches of water head.

- tion of the invention have been hereinshown and described, but it will be understoodthat numerous details of the construction shown I may be altered or omitted without-departing from the spirit of this inventionas defined the following claims.

- I claim;

1. A gage of-the Utube type comprising a'transparen'ttube and acontainer disposedat an' angle to'each other and connected to A specific embodiment and one modificagether by a soft metal tubeto form the legs respectively of the U-tube, said soft metal tube being bendable for accurately adjust-.-

ing the angular disposition of said legs with respect to each other. j

2. A gage of the U-tube type having one leg of relatively'large sectional area and having a second leg made up of inclined parallel tubes of-whic'h the combined sectional area 'is relatively small and each of which is of substantially uniform. sectional area throughout, one of said inclined tubes being transparent'and of such diameter that the surface of liquid therein will provide a meniscus disposed substantially at right angles to the length of the tube.

3. A gage of theU-tube type wherein one of the legs consists ofatransparent portion.

and an auxiliary portion extending-in paral- 'lelrelation to each other so as to'havesubstantially the same range of movement of the liquid level therein whereby the transparent portion may be ofsmall diameter compared with the total transverse area of said leg, and filler means insertible into said auxiliary portion for adjusting the free sectional area thereof throughout the range of the nor-- mal movement of the liquid level. therein, said tubes and filler meansbeing respectively of uniform sectional area'throughout.

4:. The method of adjusting a U-tube gage, one of the legs of which is made of commermay have-slightlydifl'erent internal crosssectional. areas, such 'method consisting in making the other sleg. of greater internal.

cross-sectional area than would-otherwise .be required, and then reducingsuch area byinserting insuch leg filler means, the crosssectional area ofwhich is constant through out the range of movement of the surface of cial glass. tubing, difierent lengths of which the liquidtherealong and is such as to com-.-

p'en'sate for the deviation oi the .bore of the commercial tube from the standard demanded; v

I no '5 A gage of the -U-tube type having the legs thereof-of difierent diameters andgeach being of substantially uniform cross section throughout the range-of the normal move I merit of the liquid levels therein, and filler means-inserted into one of saidlegsffor ad-' justing the relative transverse areas ofsaid- .legs and thereby adjusting the range of movement ofthe liquid undenvariationsof pressure, said filler means being'o'f substanmeans at onesidefof said contracted opening.

'6, In a gage oftheclass described,- a U- --.tube-havi'ngone leg thereof in the form of an upright bottle, a tube of smaller diameter than said bottle connected to th top thereof 'in alinement therewith, and extending below the'mouth of the bottle, and filler means for adjusting the transverse area of said bottle and confined between thew'all of said bottle and the part of said tube which extends into the same.

7. In agage of the class described, a U- tube having) one leg thereof in the form of an upright ottle, a tube of smaller diameter than said bottle connected to the top thereof in alinement therewith and extending below the mouth of the-bottle, and filler means for adjustin the transverse area of said bottle andcon ned between the wall of said bottle and the part of said tube which extends into the same, said tube having a drain-hole therein adjacent to the top of the bottle whereby when the bottle is inverted, the

liquid contents thereof may be entirely drained out.

'LEwIs COOK.

Signed at Chicago this 28th day of May, 18. I 

